1. Field of the Invention
The present invention relates to a variable compression ratio engine including a connecting rod with one end connected to a piston via a piston pin, a subsidiary arm with one end rotatably connected to the other end of the connecting rod and connected at a crankshaft via a crank pin, an eccentric shaft provided at an eccentric position of a rotary shaft rotatably supported at an engine body, and a control rod with one end connected to the subsidiary arm at a position deviated from the connecting position of the connecting rod and the other end rotatably connected to the eccentric shaft.
2. Description of the Related Art
Conventionally, such an engine is already known from, for example, Japanese Patent Application Laid-Open Nos. 9-228858 and 2000-73804, wherein the compression ratio is changed by restricting and holding the rotation position of the rotary shaft including the eccentric shaft in a plurality of rotation phases.
In the above-described conventional engines, an actuator such as an electric motor or a cylinder is connected to the rotary shaft. Since a tensile load and a compression load act on the control rod due to combustion and inertia of the engine, an impact load acts on the actuator, and therefore a means for relieving such impact is required to be provided between the actuator and the rotary shaft, thus complicating the construction.
If the rotational direction of the rotary shaft is restricted to one direction, the rotary shaft can be rotated in the one direction by utilizing the tensile load and compression load acting on the control rod by the combustion and inertia of the engine. With this construction, the actuator for driving the rotary shaft is not required. In this case, however, a restricting means for restricting and holding the rotary shaft in a plurality of rotation phases is necessary, and when such a restricting means is provided, it is desirable to prevent an impact load from acting on the contact portion between the restricting means and the rotary shaft.